Folding rule and method of manufacturing the same



Jan. 20, 1970 G. MATHES 3,490,143

FOLDING RULE AND METHOD OF MANUFACTURING THE SAME Filed July 18, 1968 2 Sheets-Sheet 1 O 0 %1A qjg ia gqg A I INVENTOR. Gamer Mat/fies lax W Mzh/ Jan. 29, 1970 G. MATHES 3,490,148

FOLDING RULE AND METHOD OF MANUFACTURING THE SAME Filed July 18, 1968 2 Sheets-Sheet 2 I NVEN TOR.

Giff? they Mathe-S United States Patent Int. Cl. GOlb 3/06; B431 7/06 US. Cl. 33105 18 Claims ABSTRACT OF THE DISCLOSURE A folding rule composed of a series of rule sections, wherein each elongated rule section has opposed end regions overlapping the end regions of an immediately preceding and an immediately following rule section to provide pairs of overlapping end regions. These pairs of overlapping end regions are each formed with aligned openings receiving a pin pivotally interconnecting the respective ruled sections, and each pin has one end engaging one of the overlapping pairs of end regions and an opposed end carrying a spring which engages the other of the pair of overlapping end regions to provide for resilient axial yieldability of the pin in the aligned openings of the overlapping end regions. The elongated rule sections are made of plastic and have integral detent means at the overlapping end regions releasably holding the rule sections in a pair of opposed positions displaced angularly by 180 with respect to each other for each pair of successive rule sections. The detent means causes resilient yielding of each pin along its axis during turning of the rule sections one with respect to the other between the positions thereof.

BACKGROUND OF THE INVENTION The present invention relates to folding rules.

It relates, for example, to a carpenters folding rule which conventionally is provided with a series of elongated rule sections where each rule section has opposed end regions overlapping the end regions of an immediately preceding and immediately following rule sections, with these end regions being pivotally interconnected with each other. The overlapping pairs of end regions of the series of rule sections are conventionally pivotally connected by suitable pins, and detent devices are provided for releasably holding the rule sections one with respect to the next in a pair of opposed angular positions displaced by l80 with respect to each other.

The rule sections may be made of plastic and the detent structures are in the form of projections and corresponding recesses into which the projections can snap. The pins which pivotally interconnect each pair of successive rule sections are provided with a yieldable resilient axial movement while engaging at one end one of each pair of overlapping end regions of the rule sections.

A known folding rule of this type has rivets which interconnect each pair of successive rule sections. Inasmuch as such a connection is relatively rigid, the detent structure formed by coacting projections and recesses is subjected to a relatively great pressure during unfolding of the folding rule, with the result that there is a considerable abrasion particularly at the edges of the detent projections and recesses. In order to reduce such abrasion it becomes necessary to add to the plastic material components which will provide a particularly hard exterior surface. The result is an undesirable increase in manufacturing costs, approaching those of folding rules made of wood. In

ice

addition, there are further complications in that in some cases it becomes necssary to provide a lubricant for the surfaces which slideably engage each other.

It is also known to provide folding rule sections made of plastic, each being formed with a groove which receives a metallic hinge structure that has a springy construction. The latter type of construction, particularly at the pivotal interconnections between the rule sections, has the disadvantage of being undesirably expensive because of the required large number of individual components which must be separately manufactured and assembled by complicated operations.

SUMMARY OF THE INVENTION It is accordingly a primary object of the present invention to provide a structure and a method which will avoid the above indicated drawbacks.

More specifically, it is an object of this invention to provide an inexpensive structure composed of a relatively small number of components which can be very quickly and easily assembled.

It is a further object of my invention to provide a simple folding rule the manufacture of which is simplified, and which will have a long operating life during which the components of the folding rule will coact properly with each other. The structure of the invention can be manufactured in suitable assembly lines by mass production techniques so as to keep the cost low.

The folding rule of the invention includes bendable spring elements which serve to retain the pivot pins in their proper positions while giving them a yieldable springy movement, the bendable springs being received in bores or other suitable openings formed in the pivot pins.

In order to enable the manufacture of my folding rule in a fully automatic manner, the pins are transversely grooved for receiving the spring, at least at one of their ends.

To achieve the springy mounting for the pin the latter may have one end, such as a head end, engaging one of each pair of overlapping end regions of the successive rule sections, while the other end of each pin is formed with a transversely extending groove receiving the bendable spring which presses against the other of each pair of overlapping end regions of the rule sections.

The bendable spring can take the form of a straight length of spring wire extending, for example, through a transverse bore adjacent an end of each pin and received in a groove formed in one of each pair of overlapping end regions of the rule sections.

To provide the successive rule sections with a construction enabling them to act one with respect to the other as bearings and supports for each other, each pair of overlapping end regions of the rule sections are provided one with a projection in the form of an annular ring surrounding the pin, and the other with a corresponding annular recess receiving the annular projection.

It is of advantage, in connection with the invention, to provide a construction wherein the assembled condition of the folding rule the pivot pins, which pivotally interconnect the sections and are slotted or notched at least at one of their ends to receive the springs, are permanently deformed for the purpose of narrowing the grooves or the like which receive the springs so as to better retain the latter.

BRIEF DESCRIPTION OF THE DRAWINGS The invention as illustrated by Way of example in the the accompanying drawings which form part of this application and in which:

FIG. 1A is a fragmentary elevation of a folding rule according to the invention, showing one complete rule section and the end regions of adjoining rule sections, with these end regions overlapping the one rule section which is completely shown;

FIG. 1B is a view of the structure of FIG. 1A as seen from the left side of FIG. 1A, with the the structure at an overlapping pair of end regions of successive rule sections illustrated in section;

FIG. 2A is a fragmentary illustration on an enlarged scale, as compared with FIGS. 1A and 1B, of an inner surface of an end region of a rule section;

FIG. 2B is a fragmentary illustration of an end region of a rule section at the inner surface thereof, which coacts with the inner surface of the end region shown in FIG. 2A;

FIG. 2C is a fragmentary exploded longitudinal section showing how the components of FIGS. 2A and 2B coact with each other when assembled;

FIG. 3 is a transverse sectional elevational on an enlarged scale as compared to the previous figures, showing the pivotal interconnection between a pair of successive rule sections at the end regions thereof and illustrating in particular the construction just before a spring is introduced into a pin opening;

FIG. 4 shows a pivot pin before assembly;

FIG. 5 illustrates the condition of the pivot pin after assembly with a spring operatively connected thereto, the rule sections being omitted from FIG. 5 for the sake of clarity, and the spring being shown in section;

FIG. 6 shows in elevation another embodiment of a pin for pivotally interconecting a pair of successive rule sections; and

FIG; 7 shows the pin of FIG. 6 after assembly with a spring.

DESCRIPTION OF PREFERRED EMBODIMENTS FIGS. 1A and 1B show only one complete rule section and end regions of a pair of adjoining rule sections. It will, of course, be understood that in a given folding rule there are a considerably gerater number of rule sections forming a longitudinal series when the folding rule is unfolded and capable of being folded to a collapsed condition in which the several rule sections are situated one over the other for substantially overlapping each other along their entire lengths, whereas in the illustrated position the successive rule sections overlap each other only at their end regions where they are pivotally interconnected.

The rule section 2 which is shown in its entirety overlaps in one end region an immediately preceding rule section 1 and in an opposed end region and immediately following rule section 3, only the end regions of the rule sections 1 and 3 being illustrated where these end regions overlap the opposed end regions of the rule section 2. It is to be noted that the end region of the section 2, which overlaps the end region of the section 1, cloacts with the latter in precisely the same way as the end region of section 3 coacts with the end region of section 2. The structure has at each pair of overlapping end regions identical features. Each pair of overlapping end regions are formed with aligned coaxial bores passing therethrough and receiving a pivot pin 4 by which the overlapping end regions are pivotally interconnected.

Each pivot pin 4 has a head end 5 which engages and is received in a recess formed in the outer surface of one of each pair of overlapping end regions. In the embodiment illustrated in FIGS. 1A-2C the end of each pin 4 opposed to its head end 5 is formed with a transverse bore 6 through which a bendable spring member 7 extends, the spring member 7 being in the form of a straight length of a wire spring.

As is apparent from FIGS. 1A, 1B and 2C, the bendable spring 7 has opposed elongated portions extending freely beyond the pin 4 and received in a groove 8 which is formed in the exterior surface of each pair of overlapping end regions, that opposes the exterior surface 4 where the head end 5 of the pin 4 is located. It should be noted that the longitudinal groove 8 formed in the exterior surface of one of each pair of overlapping end regions has a minimum depth at its opposed ends where the extremities of the spring 7 are located and becomes gradually deeper toward the pin 4.

As is indicated in FIGS. 2A to 2C, the inner surfaces of each pair of overlapping end regions which are directed toward each other are provided one With an annular ring-shaped projection 9 surrounding the pin 4 and the other with a mating annular depression or recess 10 which receives the annular projection 9. The coacting projection 9 and recess 10 concentrically surround and are located directly next to the pin 4.

The releasable detent means for releasably holding the rule sections either in the unfolded or folded positions takes the form of a pair of detent projections 11 situated at the inner surface of one of the overlapping pair of rule sections, and of a pair of coacting depressions 12 sitauted at the inner surface of the other of the pair of overlapping end regions. The detent projections 11 can be received in the detent depressions 12 in either one of a pair of positions of the end regions when they are displaced by with respect to each other.

As can best be seen in FIG. 2C, the head end 5 which is countersunk into a recess formed in the exterior surface of the end region of section 3 has an exterior concave surface bulging to a slight extent outwardly beyond the exterior surface of the section 3. The opposed end face of the pin 4 also projects to a slight extent beyond the exterior surface of the section 2. The transverse bore 6 is situated close to the referred to opposed end face of the pin 4. Preferably, the pin 4 is made of a plastic material.

As was pointed out, the groove 8 which receives the spring 7 has a minimum depth at its end regions and a maximum depth at its central region while having straight-line sloping portions between these end regions and the central region, thus providing the gradual increase in depth from the end regions toward the center region of the groove 8. The opposed ends of the spring 7 are received in the end regions of the groove 8. This construction of the groove 8 permits an axial movement of the pin 4 to take place with respect to the section 2 in opposition to the force of the spring 7 so that in this way a yieldable resilient movement of the end regions of sections 2 and 3 toward and away from each other at the location of pin 4 is achieved. The bendable spring 7 may have the form of a wire of circular cross section or of a narrow spring ribbon of polygonal cross section.

The annular projection 9 of the section 2 provides together with the recess 10 of the section 3 the equivalent of a hinge structure which prevents longitudinal shifting of the sections with respect to each other. Both of the sections 2 and 3 are turnable about the pin 4, with the section 3 being also turnable about the projection or ring 9 which forms the equivalent of a short pivot pin. Of course, an identical mutual interaction is achieved when the section 2 is turned with respect to the section 3, while the pin 4 and the spring 7 coact to provide along the axis of the pin 4 a yieldable spring pressure holding the overlapping end regions together and pressing against each other. It is preferred to provide for the annular projection 9 a depth which will situate its exterior flat surface in a plane normal to the axis of the pin 4 and situated somewhat beyond the plane of the inner surface of the section 2 so that between each pair of successive sections of the rule there will be a flat narrow gap.

The coacting detent projections 11 and depressions 12 of the sections 2 and 3, respectively, have a tapered wedge-shaped configuration and inclined side surfaces. As a result of these features, it is possible on the one hand for the projections to reliably snap into the depressions while on the other hand it is easy to displace the projections 11 out of the recesses 12.

The inner surface of the section 3 is additionally formed with a pair of small depressions 13 which, during relative turning of the sections 2 and 3, will receive the tips of the detent projections. The pair of depressions 13 are situated along an axis which is at a ring angle to the axis along which the depressions 12 are located, so that after the successive rule sections 2 and 3 have been turned one with respect to the other through 90 there will be a weakened detent connection between the successive rule sections while they are situated at a right angle one with respect to the other.

In the manufacture of the above described folding rule, there are the advantages that all of the rule sections have an identical construction and that each rule section, together with its projections, depressions, and bores, as well as its longitudinal groove is formed in a single operation and into a single body of plastic material as, for example, by injection molding. In addition to the rule sections, the folding rule requires at each pair of overlapping end regions of the rule sections only a pair of additional elements, namely, the pin 4 and the spring 7, which in themselves have a simple construction.

Furthermore, the assembly of the individual rule sec tions to form the folding rule is quite simple since only the pin 4 is required at each pair of overlapping end regions of the rule sections to be passed through the aligned bores of these end regions, while the wire spring 7 need then only be placed in the longitudinal groove 8 upon being passed through the transverse bore 6 of the pin 4.

The folding and unfolding of my folding rule takes place in a conventional manner, but because of the axial resilient mounting of the pins 4 at the interconnection of successive rule sections, the folding and unfolding operations are considerably facilitated inasmuch as, upon turning of one section with respect to another from a position which is held by the detent means, the detent projections 11 can be raised in opposition to the force of the spring 7. As a result of the small degree of friction between the sliding components of the rule during folding and unfolding thereof, particularly at the edges of the detent projections 11 and depressions 12 there is, as compared with conventional folding rules, not only a more convenient, more effortless utility of the folding rule, but in addition there is an achievement above all of an extremely low wear.

It is further to be noted that inasmuch as at each pivotal interconnection at a pair of overlapping end regions of a pair of rule sections there is the annular projection 9 which in fact forms a pin of a diameter greater than that of the pin 4, the pivotally interconnected components are guided for turning movement one with respect to the other in a highly precise manner even under conditions of severe use, and this precision in the guiding, even under the latter conditions, is far beyond what can be achieved with a thin pin or rivet that serves to interconnect a pair of successive sections of a folding rule both longitudinally as well as transversely.

In addition, the annular projection 9 enables an intermediate space to be created between a pair of successive rule sections which are pivotally connected to each other, without the use of additional washers, shims or the like, so that the danger of damaging scales printed on the rule sections is greatly reduced, such damage to the printed scales being brought about in conventional rules as a result of the turning of the rule sections with respect to each other when they rub against each other as well as a result of rough use of the rule section in its folded condition. The result of protecting the printing on the rule sections in the folded condition of the rule is also contributed to by the slightly projecting convexly curved end surfaces at the head end of each pin 4. Also, the folding rule of my invention has the advantage of enabling the scale which is printed or otherwise mounted on the rule sections to continue without interruption along the edges of the folding rule because of the structure of the pivotal interconnection and detent elements according to the invention.

Referring now to FIG. 3, it will be seen that the pair of rule sections 2 and 3 are shown in a transverse section interconnected by the pin 4 which extends through aligned openings in these rule sections which preferably are made of plastic. The rule sections are pivotally connected to each other. The head 5 of the pin 4 is countersunk into the rule section 3 at its exterior surface. In this construction, the length of the pin is selected in such a way that upon assembly of a pair of successive rule sections at their overlapping end regions, the end of the pin 4 distant from its head 5 is practically flush with the exterior surface of the rule section 2. The free end of the pin 4 is formed wih a transverse groove extending across the pin 4 transversely to its axis, this transverse groove having a keyhole configuration in cross section, according to which the inner part of the groove which is of circular cross section forms the transverse bore 6 which, however, communicates with the exterior end face of the pin 4 through the elongated narrower portion 15 whose width is smaller than the portion 6 of circular cross section. Along its outer longitudinal edges the transverse groove has beveled surfaces 16 which taper inwardly toward the narrowest part 15 of the groove.

This construction of the end of the pin, which receives the spring 7, enables a fully automatic assembly of the folding rule to be achieved since the bendable wire spring 7 which preferably has a circular cross section no longer need be advanced longitudinally through a transverse bore 6, but instead can be introduced along the axis of the pin 4 toward the lower end face thereof, as viewed in FIG. 3, in the direction of the arrow 18, with the spring 7 being pressed through the narrow part 15 of the transverse groove to be received in the bore 6 into which it is thus pressed. The construction of the pin 4, both with respect to the material of which it is made and also in some cases by providing it with grooves or the like to achieve weakened sections, is such that upon pressing of the spring 7 into the bore 6 the side surfaces which define the passage 15 will become elastically deformed and after entry of spring 7 into the bore 6 again spring back to their unstressed initial condition, so that the spring 7 is reliably held in the bore 6 and achieves a secure connection of a pair of successive rule sections.

Breaking of the spring 7 out of the bore 6 during normal loading of the folding rule is thus rendered impossi ble. The beveled surfaces 16 serve to bring about elastic deformation of the surfaces which define the passage 15 without damaging these surfaces as well as to achieve an easier introduction and pressing of the spring 7 into the bore 6 with the requirement of lesser forces than would be required if the beveled surfaces 16 were not present. These beveled surfaces enable all the respective operations to be carried out without damaging the entrance edges of the pin 4 where the wire 7 is introduced. It is, of course, possible also to provide suitable openings and springs on both ends of the pin 4 to enable the spring 7 to be assembled with the construction.

With the embodiment of the invention which is illustrated in FIGS. 4 and 5 there is also a transverse bore 6 forming part of a groove extending across the axis of the pin 4' inwardly from its end face opposed to its head 5', since in this embodiment the transverse bore 6 communicates with the exterior end face of the pin 4' through a narrow elongated passage 20 the width of which is smaller than the diameter of the circular cross section of the bore 6. At their regions adjacent the exterior end surface of the pin 4', the side surfaces which define the passage 20 terminate in beveled surfaces forming parts of a pair of raised projections 22 and 23, as indicated in FIG. 4. It is also possible, according to the cross section of the spring 7, to provide the bore 6 with a cross section which is not circular but matches that of the spring 7, or the spring 7, in a manner similar to a Seger ring, may circumferentially surround the pin 4' which in this case would be formed with a lateral slit. In this latter construction the inwardly extending groove, slit, or the like which receives the spring would have a construction at the side surface of the pin 4 which would enable the opening to be closed, after introduction of the spring, by suitable tools.

After the pin 4' is introduced into the aligned openings of a pair of overlapping end regions of a pair of rule sections, the spring 7 is pushed into the transverse bore 6, and then a suitable stamping or pressure tool 25, shown in phantom lines in FIG. 5, subjects the pin 4 to an axial pressure acting on the raised portions 22 and 23 so that by cold-forming of the latter they are pressed toward the head end of the pin and thus narrow the passage into the passage 26 indicated in FIG. 5. By a suitable configuration for the raised projections 22 and 23, it is possible when pressing the latter toward the head end 5 with a tool such as the tool to achieve a construction where the passage 20 is practically closed with the surfaces which formerly defined the passage 20 engaging each other.

Furthermore, with a suitable material for the pin 4', it is possible to achieve hot-working instead of cold working so that the deformation of the material takes place under heat and pressure. The latter type of operation will particularly be used in the case where the pin 4 is made of a plastic material. Thermoplastic materials can be worked under pressure without any additional heat in order to be shaped in the above described manner.

In FIGS. 6 and 7 there is a further embodiment of a pin 4a, according to which, after assembly of the pair of overlapping end regions of a pair of successive rule sections and the spring 7, the pin 4a is deformed with a fork-- shaped stamp 28, shown in phantom lines in FIG. 7, in such a way that the passage 15 leading to the bore 6 is at least partly closed to prevent the spring 7 from breaking out of the bore 6 even under intense stressing.

This embodiment of the spring-receiving end of the pin 4a and the subsequent deformation by the tool 28 assure a fully automatic assembly of the folding rule, even when using plastic pins or pins of similar material, manufactured, for example, by injection molding or diecasting, since the bendable wire spring 7 which preferably is in the form of a length of wire of circular section need not be directed axially through a bore 6, but instead can be pressed in along the axis of the pin 4a from the end face thereof opposed to the head 5a into the bore 6 while passing through the passages such as the passage 20 of FIG. 4 or the passage 15 of FIG. 6. The deformation or upsetting of the pins 4a and 4' after the spring 7 has thus been pushed into the bore 6 so as to narrow or close the passage 15 and 20, respectively, assures a high-quality strong connection between the pin and the spring 7 so that deflection of the spring out of the bore is not to be feared.

By using plastic for the rule sections, it becomes necessary in order to carry out a fully automatic manufacturing of the folding rule to provide only the molding compounds, the required bolts or pins 4, and springs, whereupon a fully automatic manufacture can take place, with the folding rules being packed in finished condition to leave the automated line of manufacture and packing in condition ready for shipment.

Many thermoplastics with and without fillers can be used for the manufacture of the sections of the folding rule of the invention. In the event that the modulus of elasticity of such a plastic is not sufficiently great, then the thermoplastic material can be reinforced with glass fibers. For example, it is possible to achieve the desired results with materials, such as a suitable polyamide reinforced with glass fibers and having a modulus of elasticity of approximately from 60,000 up to over 120,000 kg./ cm

I claim:

1. In a folding rule, a series of elongated rule secregions of immediately preceding and immediately fol-' lowing rule sections to form overlapping pairs of end regions, each overlapping pair of end regions being formed with coaxial openings passing therethrough, and having integral releasable detent means for releasably holding successive rule sections in a pair of positions where successive sections are displaced by one with respect to the other, a pin extending through the coaxial openings of each overlapping pair of end regions and having one end engaging one of said end regions and an opposed end formed with an opening, and a bendable spring member situated in said opening of said pin and providing a resilient yieldable axial movement of said pin with respect to said overlapping end regions While retaining said pin assembled with said end regions for pivotally interconnecting the latter.

2. The combination of claim 1 and wherein said spring is in the form of a substantially straight wire spring member terminating in elongated portions extending beyond said pin on opposite sides thereof and engaging the exterior surface of one of each pair of overlapping end regions, said exterior surface being formed with a groove in which said spring member in situated, and said pin opening being a bore passing through said pin.

3. The combination of claim 2 and wherein said groove has opposed ends of minimum depth situated distant from said pin and said groove having a gradually increasing depth from said opposed ends thereof toward said pin.

4. The combination of claim 1 and wherein each pair of overlapping end regions have inner faces directed toward each other, one of said inner faces of each pair of overlapping end regions being formed with an annular recess surrounding said pin and the other of each pair of said end regions having at its inner face an annular projection surrounding said pin and adapted to be received in said annular recess.

5. The combination of claim 1 and wherein said opening of said pin is in the form of an elongated groove extending into said pin, and said spring being received in the innermost part of said groove while said pin has outwardly beyond said spring permanently deformed portions narrowing said groove at its region beyond said spring to a width less than its initial width for retaining the spring reliably in said groove.

6. The combination of claim 1 and wherein said rule sections are made of reinforced plastic.

7. The combination of claim 6 and wherein said rule sections are reinforced with glass fibers.

8. The combination of claim 1 and wherein said pin which interconnects each pair of overlapping end regions has opposed to its end which engages one of said end regions an end face from which said opening of said pin, in which said spring is retained, extends inwardly into said pin.

9. The combination of claim 8 and wherein said opening has in the region of said end face a relatively narrow elongated portion extending transversely across the pin and inwardly of said narrow elongated portion an inner portion of larger cross section in which said spring is located.

10. The combination of claim 9 and where said pin is provided at said end face with beveled parallel surfaces extending inwardly from said end face and defining a tapered portion of the narrow portion of said opening.

11. The combination of claim 9 and wherein said pin is formed at predetermined parts of its cross section with weakening narrowed portions providing yielding of said pin at said weakening narrowed portions thereof during introduction of a spring through the narrow portion of said opening into the inner part which is larger in section than said narrow portion thereof.

12. The combination of claim 9 and wherein said pin is made of plastic.

13. The combination of claim 9 and wherein said narrow portion of said opening is defined by a pair of surfaces directed toward and engaging each other for retaining the spring in said opening.

14. In a method of assembling components of a folding rule, the step of passing through aligned openings of a pair of overlapping end regions of successive sections of the rule a pin which at one end is formed with a slot extending transversely across the pin inwardly from an end face thereof at said one end at said pin, pressing a wire spring member into said slot to situate said spring member inwardly beyond said end face of said pin, and then pressing toward each other parts of said pin at said end face thereof where said slot is located to narrow said slot outwardly beyond said spring for retaining the latter assembled with said pin.

15. In the method according to claim 14, applying a pressing tool to said end face of said pin for narrowing said slot thereof beyond said spring.

16. The method of claim 15 and wherein said tool cold-works said pin.

17. In a method as recited in claim 15 and wherein References Cited UNITED STATES PATENTS 2,663,940 12/1953 GaSStrOm et al 33119 2,713,206 7/1955 Zelnick 33-115 FOREIGN PATENTS 880,215 6/1953 Germany.

HARRY N. HAROIAN, Primary Examiner US. Cl. X.R. 

